Vaccination

Vaccination

Definition

Vaccination introduces a vaccine into the body to produce immunity and prevent specific diseases.

Description

Many diseases that once caused widespread illness, disability, and death are now prevented by vaccines in developed countries. Vaccines are medicines that contain weakened or dead bacteria or viruses. When a child receives a vaccine, his or her immune system responds by producing antibodies, substances that weaken or destroy disease-causing organisms. When the child comes in contact with live bacteria or viruses of the same kind that are in the vaccine, the antibodies prevent those organisms from making the child sick. Vaccines also stimulate the cellular immune system. In other words, the child becomes immune to the disease the organisms normally cause. Building immunity by using a vaccine is called immunization. Childhood immunizations are safe and remain the most effective way to prevent disease.

Vaccines contain antigens (weakened or dead viruses, bacteria, and fungi that cause disease and infection). When introduced into the body, the antigens stimulate the immune system response by instructing B cells to produce antibodies, with assistance from T-cells. The antibodies are produced to fight the weakened or dead viruses in the vaccine. The antibodies "practice" on the weakened viruses, preparing the immune system to destroy real and stronger viruses in the future. When new antigens enter the body, white blood cells (called macrophages) engulf them, process the information contained in the antigens, and send it to the T-cells so that an immune system response can be mobilized.

General use

In the early 2000s, children in the United States and in other developed countries routinely have a series of vaccinations that begins at birth. Vaccinations in children began about 1900 with the smallpox vaccine. In 1960 there were only five vaccines in eight shots. The number of vaccinations children receive has steadily increased since that time. As of 2004, children receive 11 different vaccines given in up to 20 shots by age two years. Given according to a specific schedule, these vaccinations protect against hepatitis B ; diphtheria , tetanus , pertussis (whooping cough ) (DTP); measles , mumps , rubella (German measles); varicella (chickenpox ); polio ; pneumococcus; and Haemophilus influenza type B (Hib disease, a major cause of spinal meningitis ) and, in some states, hepatitis A . This series of vaccinations is recommended by the American Academy of Family Physicians, the American Academy of Pediatrics, and the Centers for Disease Control and Prevention and is a requirement in all states before children can enter school. States make exceptions for children who have medical conditions such as cancer that prevent them from having vaccinations, and some states also make exceptions for children whose parents object for religious or other reasons.

Several vaccines are delivered in one injection, such as the measles-mumps-rubella (MMR) and diphtheria-tetanus-pertussis (DTP) combinations.

Vaccines are used in several ways. Some vaccines, such as the rabies vaccine , are given only when a child comes in contact with the virus that causes the disease, such as through a dog bite.

Recommendations for other vaccines and immunobiologic medicines depend on the child's health status or area of world where the family might travel. Such treatments are vaccine or immune globulin for hepatitis A, typhoid, meningitis, Japanese encephalitis , and rabies .

In addition the uses discussed above, vaccines are available for preventing anthrax, cholera, plague, tuberculosis , and yellow fever. Most vaccines are given as injections, but a few are taken orally.

The administration of vaccines to meet travel requirements should not interfere with or postpone any

source:Department of Health and Human Services Centers for Disease Control and Prevention, 2005.

Hepatitis B

HepB #1

HepB #2

HepB #3

HepB Series

Diphtheria, Tetanus, Pertussis

DTaP

DTaP

DTaP

DTaP

DTaP

Td

Td

Haemophilus influenzae type b

Hib

Hib

Hib

Hib

Inactivated Poliovirus

IPV

IPV

IPV

IPV

Measles, Mumps, Rubella

MMR #1

MMR #2

MMR #2

Varicella

Varicella

Varicella

Pneumococcal

PCV

PCV

PCV

PCV

PCV

PPV

Influenza

Influenza (yearly)

Influenza (yearly)

of the routine childhood immunizations. If necessary, the routine immunization schedule can be accelerated to give as many vaccines as possible before departure. Decisions about vaccinations for children with chronic illnesses are made with the child's doctor.

Parents who are planning to travel with children to another country should find out what vaccinations are needed. Some vaccinations may be needed 12 weeks before the trip, so getting this information early is important. Many major hospitals and medical centers have travel clinics that provide this information. The traveler's health section of the Centers for Disease Control and Prevention also has information on vaccination requirements.

A vaccination health record helps parents and healthcare providers keep track of a child's vaccinations. The record should start when the child has his or her first vaccination and should be kept up-to-date with each added vaccination. While most doctors follow the recommended vaccination schedule, some flexibility is allowed. For example, vaccinations scheduled for age two months may be given anytime between six to ten weeks. Slight departures from the schedule do not keep the child from developing immunity, as long as all the vaccinations are received close to the right times.

Precautions

Vaccines are not always effective, and there is no way to predict whether a vaccine will "take" in any particular child. To be most effective, vaccination programs depend on the whole community participating. An increase in the number of vaccines given to children and the increased percentage of children receiving vaccines has resulted in a dramatic decrease in the number of vaccine-preventable diseases. In the United States, most young parents as of 2004 had never seen many of diseases that vaccines prevent. Even people who do not develop immunity through vaccination are safer because their friends, neighbors, children, and coworkers are immunized.

Factors influencing recommendations for childhood vaccination include age-specific risks of disease and
complications, the ability of a given age group to respond to the vaccine, and the potential interference with the immune response to transferred maternal antibody. There are vaccines for the youngest age group at risk for developing the disease and known to develop a satisfactory antibody response to the vaccination.

Like most medical procedures, vaccination has risks as well as great benefits. When children receive a vaccine, parents should be told about both. Questions or concerns should be discussed with a doctor or other healthcare provider. The Centers for Disease Control and Prevention, located in Atlanta, Georgia, is also a good resource for information.

Vaccines may cause problems for children with certain allergies . Children who are allergic to the antibiotics neomycin or polymyxin B should not take rubella vaccine, measles vaccine, mumps vaccine, or the combined measles-mumps-rubella (MMR) vaccine. Children who have had a severe allergic reaction to baker's yeast should not take the hepatitis B vaccine . Patients who are allergic to antibiotics such as gentamicin sulfate, streptomycin sulfate, or other amino glycosides should check with their doctors before the taking influenza vaccine, as some influenza vaccines contain small amounts of these drugs. Also, some vaccines, including those for influenza, measles, and mumps, are grown in the laboratory in fluids of chick embryos, and should not be given to children who are allergic to eggs. In general, parents of children who have had an unusual reaction to a vaccine in the past should report the reaction to the doctor before taking the same vaccine again. Doctors need to know about allergies to foods, medicines, preservatives, or other substances.

Children with other medical conditions should be given vaccines with caution. Influenza vaccine may reactivate Guillain-Barre syndrome (GBS) in patients who have had it before. This vaccine also may worsen illnesses that involve the lungs, such as bronchitis or pneumonia . Vaccines that cause fever as a side effect may trigger seizures in people who have a history of seizures caused by fever.

Certain vaccines are not recommended during pregnancy. However, women who are at risk of getting specific disease such as polio may receive the vaccine to prevent medical problems in their babies. Vaccinating a pregnant woman with tetanus toxoid can prevent tetanus in the baby at birth.

Women should avoid becoming pregnant for three months after taking rubella vaccine, measles vaccine, mumps vaccine, or the combined measles-mumps-rubella (MMR) as these vaccines may cause problems in the unborn baby.

Women who are breastfeeding should check with their doctors before taking any vaccine.

Side effects

Most side effects from vaccines are minor and easily treated. The most common are pain , redness, and swelling at the injection site. Some children may also develop a fever or a rash. Rarely, vaccines may cause severe allergic reactions, swelling of the brain, or seizures. Unusual reaction after receiving a vaccine should be reported to the doctor right away.

Interactions

Vaccines may interact with other medicines and medical treatments. When this happens, the effects of the vaccine or the other medicine may change or the risk of side effects may be greater. Radiation therapy and cancer drugs may reduce the effectiveness of many vaccines or may increase the chance of side effects. Parents should let the doctor know of all medicines taken by the child and learn whether the possible interactions could interfere with the therapeutic effects of the vaccine or the other medicines.

Parental concerns

All vaccines used for routine child vaccinations in the United States may be given simultaneously. There is no evidence that simultaneous administration of vaccines either reduces vaccine effectiveness or increases the risk of adverse events. The only vaccines which should not be given at the same time are cholera and yellow fever vaccines.

Some vaccines are mixed in one solution, such as measles-mumps-rubella (MMR) and diphtheria-tetanus-pertussis (DTP) combination. A survey of the literature as of 2004 indicated no evidence supporting the idea that multiple vaccines in any way overwhelm or weaken the immune system. Most young infants have strong immune systems that are capable of responding to all the recommended vaccines. The protection from bacterial and viral infections provided by vaccines preserves the infant's immune systems to fight off other infections.

Most doctors follow the recommended vaccination schedule, with some flexibility. For example, vaccinations that are scheduled for age two months may be given anytime between six to 10 weeks. Slight departures from the schedule will not stop the child from developing immunity, as long as the child gets all the vaccinations close the right times.

KEY TERMS

Anthrax—A bacterial infection, primarily of livestock, that can be spread to humans. In humans it affects the skin, intestines, or lungs.

Antibody—A special protein made by the body's immune system as a defense against foreign material (bacteria, viruses, etc.) that enters the body. It is uniquely designed to attack and neutralize the specific antigen that triggered the immune response.

Bacteria—Singluar, bacterium; tiny, one-celled forms of life that cause many diseases and infections.

Cholera—An infection of the small intestine caused by a type of bacterium. The disease is spread by drinking water or eating foods that have been contaminated with the feces of infected people. It occurs in parts of Asia, Africa, Latin America, India, and the Middle East. Symptoms include watery diarrhea and exhaustion.

Encephalitis—Inflammation of the brain, usually caused by a virus. The inflammation may interfere with normal brain function and may cause seizures, sleepiness, confusion, personality changes, weakness in one or more parts of the body, and even coma.

Feces—The solid waste, also called stool, that is left after food is digested. Feces form in the intestines and pass out of the body through the anus.

Guillain-Barré syndrome—Progressive and usually reversible paralysis or weakness of multiple muscles usually starting in the lower extremities and often ascending to the muscles involved in respiration. The syndrome is due to inflammation and loss of the myelin covering of the nerve fibers, often associated with an acute infection. Also called acute idiopathic polyneuritis.

Immune system—The system of specialized organs, lymph nodes, and blood cells throughout the body that work together to defend the body against foreign invaders (bacteria, viruses, fungi, etc.).

Immunization—A process or procedure that protects the body against an infectious disease by stimulating the production of antibodies. A vaccination is a type of immunization.

Inflammation—Pain, redness, swelling, and heat that develop in response to tissue irritation or injury. It usually is caused by the immune system's response to the body's contact with a foreign substance, such as an allergen or pathogen.

Meningitis—An infection or inflammation of the membranes that cover the brain and spinal cord. It is usually caused by bacteria or a virus.

Microorganism—An organism that is too small to be seen with the naked eye, such as a bacterium, virus, or fungus.

Organism—A single, independent unit of life, such as a bacterium, a plant, or an animal.

Plague—A serious, potentially life-threatening infectious disease caused by the bacterium Yersinia pestis. The disease is usually transmitted to humans by the bites of infected rodent fleas. There are three major types: bubonic, pneumonic, and septicemic.

Seizure—A sudden attack, spasm, or convulsion.

Tuberculosis—Tuberculosis (TB) is a potentially fatal contagious disease that can affect almost any part of the body, but is mainly an infection of the lungs. It is caused by a bacterial microorganism, the tubercle bacillus or Mycobacterium tuberculosis. Symptoms include fever, weight loss, and coughing up blood.

Typhoid fever—A severe infection caused by a bacterium, Salmonella typhi. People with this disease have a lingering fever and feel depressed and exhausted. Diarrhea and rose-colored spots on the chest and abdomen are other symptoms. The disease is spread through poor sanitation.

Virus—A small infectious agent consisting of a core of genetic material (DNA or RNA) surrounded by a shell of protein. A virus needs a living cell to reproduce.

Yellow fever—An infectious disease caused by a virus. The disease, which is spread by mosquitoes, is most common in Central and South America and Central Africa. Symptoms include high fever, jaundice (yellow eyes and skin) and dark-colored vomit, a sign of internal bleeding. Yellow fever can be fatal.

Immunizations are not given when a child has signs of an acute illness. An interrupted primary series of immunizations need not started again but may simply continue after the child recovers. The child's doctor is the best person to decide when each vaccination should be given.

The eventual goal in child care is to reduce stress. Parents should try to increase the child's feeling of security and well-being by close involvement with the immunization process. Providing explanations of the immunization plan, special tests, and procedures suitable to the child's age is helpful. Infants and toddlers are not likely to understand verbal explanations, but they have a strong parental attachment and need affection to ease fears. Small children also have an urgent need for their mothers to defend them during medical treatments. Older children may even protest or despair in getting an injection but are usually accepting of reasonable explanations.

The health-care professional reviews the immunization record and the health status of the child at each visit. If necessary the nurse or doctor helps the parent correctly position the child and exposure of the injection site. Parents should hold a small child on their laps securely for the injection; older children may be put on the examination table in the doctor's office. After the injection, parents can give the child immediate comfort to control crying and then leave the treatment room.

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Vaccination

Gale Encyclopedia of Medicine, 3rd ed.
COPYRIGHT 2006 Thomson Gale

Vaccination

Definition

Vaccination is the use of vaccines to prevent specific diseases.

Purpose

Many diseases that once caused widespread illness, disability, and death now can be prevented through the use of vaccines. Vaccines are medicines that contain weakened or dead bacteria or viruses. When a person takes a vaccine, his or her immune system responds by producing antibodies—substances that weaken or destroy disease-causing organisms. When the person is later exposed to live bacteria or viruses of the same kind that were in the vaccine, the antibodies prevent those organisms from making the person sick. Vaccines usually also stimulate the so-called cellular immune system as well. In other words, the person becomes immune to the disease the organisms normally cause. The process of building up immunity by taking a vaccine is called immunization.

Vaccines are used in several ways. Some, such as the rabies vaccine, are given only when a person is likely to have been exposed to the virus that causes the disease—through a dog bite, for example. Others are given to travelers planning to visit countries where certain diseases are common such as typhoid fever or yellow fever. Vaccines such as the influenza vaccine, or "flu shot," are given mainly to specific groups of people—older adults and others who are at high risk of developing influenza or its complications. Then, there are vaccines that are given to almost everyone, such as the ones that prevent diphtheria, tetanus, polio and measles.

Children routinely have a series of vaccinations that begins at birth. Given according to a specific schedule, these vaccinations protect against hepatitis B, diphtheria, tetanus, pertussis (whooping cough ), measles, mumps, rubella (German measles), varicella (chickenpox), polio, pneumococcus and Haemophilus influenzae type b (Hib disease, a major cause of spinal meningitis) and, in some states, hepatitis A. This series of vaccinations is recommended by the American Academy of Family Physicians, the American Academy of Pediatrics, and the Centers for Disease Control and Prevention and is required in all states before children can enter school. All states will make exceptions for children who have medical conditions such as cancer that prevent them from having vaccinations, and some states also will make exceptions for children whose parents object for religious or other reasons.

Description

In addition to those discussed above, vaccines are available for preventing anthrax, cholera, hepatitis A, Japanese encephalitis, meningococcal meningitis, plague, pneumococcal infection (meningitis, pneumonia), tuberculosis, typhoid fever, and yellow fever. Most vaccines are given as injections, but a few are given by mouth.

Some vaccines are combined in one injection, such as the measles-mumps-rubella (MMR) or diphtheria-pertussis-tetanus (DPT) combinations.

Recommended dosage

The recommended dosage depends on the type of vaccine and may be different for different patients. The healthcare professional who gives the vaccine will decide on the proper dose.

A vaccination health record will help parents and health care providers keep track of a child's vaccinations. The record should be started when the child has his or her first vaccination and should be updated with each additional vaccination. While most physicians follow the recommended vaccination schedule, parents should understand that some flexibility is allowed. For example, vaccinations that are scheduled for age two months may be given anytime between six to 10 weeks. When possible, follow the schedule. However, slight departures will not prevent the child from developing immunity, as long as all the vaccinations are given at around the right times. The child's physician is the best person to decide when each vaccination should be given.

Anyone planning a trip to another country should check to find out what vaccinations are needed. Some vaccinations must be given as much as 12 weeks before the trip, so getting this information early is important. Many major hospitals and medical centers have travel clinics that can provide this information. The Traveler's Health Section of the Centers for Disease Control and Prevention also has information on vaccination requirements.

DT (diptheria-tetanus booster shot; and then booster shot every 10 to 15 years)

Precautions

Vaccines are not always effective, and there is no way to predict whether a vaccine will "take" in any particular person. To be most effective, vaccination programs depend on whole communities participating. The more people who are vaccinated, the lower everyone's risk of being exposed to a disease. Even people who do not develop immunity through vaccination are safer when their friends, neighbors, children, and coworkers are immunized.

Like most medical procedures, vaccination has risks as well as substantial benefits. Anyone who takes a vaccine should make that sure he or she is fully informed about both the benefits and the risks. Any questions or concerns should be discussed with a physician or other health care provider. The Centers for Disease Control and Prevention, located in Atlanta, Georgia, also is a good source of information.

ALBERT BRUCE SABIN (1906–1993)

Albert Bruce Sabin was born on August 26, 1906, in Bialystok, Russia, to Jacob and Tillie Sabin. In order to escape extreme poverty, the Sabins immigrated to the United States and settled in Paterson, New Jersey. Following his graduation from high school in 1923, Sabin was able to attend dentistry school at New York University due to his uncle's generous offer for financing. However, after reading Paul deKruif's Microbe Hunters he became intrigued by virology and the idea of curing epidemic diseases. After two years of dentistry school, Sabin decided to switch to medicine, earning his M.D. in 1931. Sabin completed his residency and internship in the United States and then went to London to conduct research.

Sabin returned to the United States in 1935 to resume his research of polio at the Rockefeller Institute. In 1953, Jonas Salk announced that he had created a dead-virus polio vaccine that was safe, but soon after its administration many people died. Sabin, however, wanted to create a live-virus vaccine, which he felt would be safer. Sabin diluted three strains of the polio virus and tested these on himself, his family, and other volunteers. These live-virus vaccines (given orally) proved safe and effective and soon became the vaccinations of choice around the world. Sabin's published works include Viruses and Cancer: A Public Lecture in Conversational Style (1965), Behavior of Chimpanzee-Avirulent Poliomyelitis Viruses in Experimentally Infected Human Volunteers (1955), and Recent Advances in Our Knowledge of Dengue and Sand Fly Fever (1955). Sabin died of congestive heart failure on March 3, 1993.

Vaccines may cause problems for people with certain allergies. For example, people who are allergic to the antibiotics neomycin or polymyxin B should not take rubella vaccine, measles vaccine, mumps vaccine or the combined measles-mumps-rubella (MMR) vaccine. Anyone who has had a severe allergic reaction to baker's yeast should not take the hepatitis B vaccine. Patients who are allergic to antibiotics such as gentamicin sulfate, streptomycin sulfate or other aminoglycosides should check with their physicians before taking influenza vaccine, as some influenza vaccines contain small amounts of these drugs. Also, some vaccines, including those for influenza, measles and mumps, are grown in the fluids of chick embryos and should not be taken by people who are allergic to eggs. In general, anyone who has had an unusual reactions to a vaccine in the past should let his or her physician know before taking the same kind of vaccine again. The physician also should be told about any allergies to foods, medicines, preservatives, or other substances.

People with certain other medical conditions should be cautious about taking vaccines. Influenza vaccine, for example, may reactivate Guillain-Barré syndrome (GBS) in people who have had it before. This vaccine also may worsen illnesses that involve the lungs, such as bronchitis or pneumonia. Vaccines that cause fever as a side effect may trigger seizures in people who have a history of seizures caused by fever.

Certain vaccines are not recommended for use during pregnancy, but some may be given to women at especially high risk of getting a specific disease such as polio. Vaccines also may be given to pregnant women to prevent medical problems in their babies. For example, vaccinating a pregnant woman with tetanus toxoid can prevent her baby from getting tetanus at birth.

Women should avoid becoming pregnant for three months after taking rubella vaccine, measles vaccine, mumps vaccine or the combined measles-mumps-rubella (MMR) as these vaccines could cause problems in the unborn baby.

Women who are breastfeeding should check with their physicians before taking any vaccine.

Side effects

Most side effects from vaccines are minor and easily treated. The most common are pain, redness, and swelling at the site of the injection. Some people may also develop a fever or a rash. In rare cases, vaccines may cause severe allergic reactions, swelling of the brain, or seizures. Anyone who has an unusual reaction after receiving a vaccine should get in touch with a physician right away.

Interactions

Vaccines may interact with other medicines and medical treatments. When this happens, the effects of the vaccine or the other medicine may change or the risk of side effects may be greater. For example, radiation therapy and cancer drugs may reduce the effectiveness of many vaccines or may increase the chance of side effects. Anyone who takes a vaccine should let the physician know all other medicines he or she is taking and should ask whether the possible interactions could interfere with the effects of the vaccine or the other medicines.

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Vaccination

Encyclopedia of Espionage, Intelligence, and Security
COPYRIGHT 2004 The Gale Group Inc.

Vaccination

United States President George W. Bush authorized a program on December 13, 2002, which by its conclusion, will see approximately 500,000 military personnel vaccinated against smallpox, along with an equal number of key healthcare providers in the United States. In the event of a biological attack that would expose Americans to smallpox, the affected citizens could then be quickly vaccinated by the protected healthcare workers. Additionally, the vaccine will be offered to up to ten million police, firefighters, and other first responders to emergencies. Smallpox vaccination within three days of exposure will usually prevent development of the disease, or dramatically reduce its virulence. Plentiful stocks are on hand in the U.S. to respond to a large smallpox outbreak, and vaccine in quantities necessary for inoculation of the entire population of the United States are in production. By mid-2004, health officials plan to have smallpox vaccinations available on a voluntary basis for all Americans.

An anthrax vaccine is also available and is only routinely given to laboratory workers who are involved with B. anthracis study or cultures. Vaccination for anthrax prevention involves a series of six injections over an 18-month period. Over 500,000 military personnel received the vaccine as a precaution in 2002, but for the general population, including medical providers and first responders, the vaccine is not currently recommended as other options such as antibiotic treatment offer protection to individuals exposed to anthrax-causing bacteria.

Diseases like anthrax and smallpox are among those microbial diseases that could be exploited as biological weapons. Indeed, anthrax was sent through the postal system to targets in the United States in the aftermath of the September 11, 2001 terrorist attacks in the U.S. Anthrax is a disease caused by the bacterium Bacillus anthracis, which can infect the skin, digestive tract, or lungs. Lung infection is often fatal. Smallpox is an extremely contagious disease that is caused by the variola virus.

Vaccination refers to the procedure in which the presence of a component of a microorganism such as a protein (the antigen) stimulates the defense mechanism of the host, which is known as the immune system, to form an antibody. Each antibody is formed in specific response to a particular antigen. The antibodies act to protect the host from future exposure to the antigen (immunity). Depending on the disease and the nature of the vaccine, the immunity can last from a year or two (i.e., influenza) to a lifetime.

Vaccination is protective against infection without the need of suffering through a bout of a disease. In this artificial process an individual receives the antibody-stimulating compound either by injection or orally. Some vaccines like that for smallpox do contain live microorganisms, which can cause some discomfort and, in rare cases, more serious complications. Nonetheless, for most people, vaccination is a prudent step to avoid the threat of a disease. As of early 2003, only one healthcare worker having received the recent smallpox vaccine reported a related complication, a non-life threatening vaccina rash. Less than a dozen instances of complication (none considered serious) have been reported among military personnel receiving the vaccine.

The technique of vaccination has been practiced since at least the early decades of the eighteenth century. Then, a common practice in Istanbul, Turkey was to retrieve material from the surface sores of a smallpox sufferer and rub the material into a cut on another person. The recipient was often spared the ravages of smallpox. This practice was noted by Lady Mary Wortley Montague, the wife of the British Ambassador Extraordinary to the Turkish court. Upon her return to England, she used her social standing to promote the benefits of this crude method of smallpox inoculation. Among those who were convinced was the Royal Family. Indeed, it became fashionable to receive an inoculation, partly perhaps it carried social cache. The technique was refined by Edward Jenner into a vaccine for cowpox in 1796.

Since Jenner's time, vaccines for a variety of bacterial and viral maladies have been developed. The material used for vaccination is one of four types. Some vaccines consist of living but weakened viruses. Such an attenuated vaccine does not cause an infection but does elicit an immune response. An example is the measles, mumps, and rubella (MMR) vaccine. The second type of vaccine can involve killed viruses or bacteria. The virus or bacteria need to be killed in a way that does not perturb their surfaces. This care is necessary to preserve the three-dimensional structure of surface molecules that stimulate the immune response. Agents such as alum can be used to enhance the immune response to the killed target, perhaps by exposing the antigen to the immune system for a longer time. A third type of vaccination involves a toxoid, which is an inactivated form of a toxin produced by the target bacterium. Examples of toxoid vaccines are the diphtheria and tetanus vaccines. Lastly, a biosynthetic vaccine can utilize a synthetic compound pieced together from portions of two antigens. The Hib vaccine is a biosynthetic vaccine.

Vaccinations against some diseases occurs early in life. For example, during an infant's first two years of life, a series of vaccinations is recommended to develop protection against hepatitis B, polio, measles, mumps, ru-bella (also called German measles), pertussis (also called whooping cough), diptheriae, tetanus (lockjaw), Haemophilus influenzae type b, pneumococcal infections, and chickenpox. Multiple injections of the vaccine can be required to ensure that the immunity that develops is long lasting. For example, vaccination against diphtheria, tetanus, and pertussis is typically administered at 2 months of age, 4 months, 6 months, 15 to 18 months, and finally at 4 to 6 years of age.

A series of vaccinations such as the above triggers a greater production of antibody by the immune system.

The immune cells that respond to the presence of an antigen in a vaccine are called lymphocytes. Prior to vaccination there are a multitude of lymphocytes, each of which recognizes a single specific protein or a portion of the protein. The presence of a specific antigen stimulates that lymphocyte that recognizes the antigenic target. That lymphocyte will then divide repeatedly and the daughter cells will produce antibody. Eventually, there are many daughter lymphocytes and a lot of antibody circulating in the body.

If the antigen does not persist in the body, the production of antibodies will stop. But the lymphocytes that have been produced still retain the memory of the target protein. When the target is presented again to the lymphocytes, as happens in the second vaccination in a series, the many lymphocytes are stimulated to divide into daughter cells, which in turn form antibodies. This is because the immune cells that responded to the antigen upon the first exposure "remember" the antigen, and so can produce even more antibody when presented with the antigen a second or third time. In immunological terms the immune cells are said to be "primed." This form of antigenic memory can last for a lifetime for diseases such as diphtheria and pertussis. For other diseases such as tetanus adults should be vaccinated every ten years (a "booster shot") in order to keep their bodies primed to fight the tetanus microorganism.

Many vaccinations are given via injection. However, solutions that can be drunk are also used. The classic example is the oral vaccine to polio devised by Albert Sabin. Oral vaccination is often limited by the passage of the vaccine through the highly acidic stomach. In the future is hoped that the bundling of the vaccine in a protective casing will prevent the damage caused in the stomach. Experiments using bags made out of lipid molecules (liposomes) has demonstrated both protection of the vaccine and the ability to tailor the liposome release of the vaccine.

While the benefits of vaccination are obvious, this protection against disease does not come without a risk. For a variety of vaccines, side effects are possible. For some vaccines, the side effects are minor. A person may, for example, develop a slight ache and redness at the site of injection. In some very rare cases, however, more severe reactions can occur, such as convulsions and high fever. The smallpox vaccine carries the risk of encephalitis (swelling of cells of the brain and spinal cord) in approximately three to 12 people per million people vaccinated.

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Vaccination

Encyclopedia of Children and Childhood in History and Society
COPYRIGHT 2004 The Gale Group Inc.

Vaccination

Chinese physicians discovered about a thousand years ago how to reduce the risk of dying from smallpox by scarifying the skin of susceptible persons with secretions from a healing smallpox bleb, thus inducing a mild attack of smallpox. This procedure, called variolation, was not without risk–about one person in a hundred sustained a severe and sometimes fatal attack of smallpox. Nonetheless it was widely used to protect the children of educated well-to-do people in China, and the procedure spread westward along the silk route. Lady Mary Wortley Montagu, wife of the British ambassador in Constantinople, described it in a 1717 letter to a friend in England and introduced it in England when she returned home.

Smallpox Vaccination

Edward Jenner, a naturalist and family doctor in the village of Berkeley, Gloucestershire, knew about variolation, and knew that milkmaids who had been infected with cowpox, a common disease of cattle in that area, never got smallpox. He reasoned that it might be possible to inoculate cowpox serum into the skin in the same way as the more risky smallpox secretions. During an epidemic of smallpox in 1796, Jenner inoculated a nine-year-old boy, James Phipps, with fluid from a cowpox lesion, and over the following months he inoculated a total of twenty-three people, mostly children, in the same way. All survived unharmed and none got smallpox. Jenner's experiment would not withstand the rigorous ethical scrutiny required for modern human experimentation, but its lasting benefits for humankind have been enormous. Jenner reported his results in An Inquiry into the Causes and Effects of the Variolae Vaccinae (1798). Vaccination is derived from vaccinae, the Latin for the possessive of vacca, or cow. Vaccine is the fluid containing weakened or dead pathogens, which stimulate immune responses that protect against contagious disease. First applied to protection from smallpox, vaccination and vaccine broadened in meaning to include all such immunizing procedures as these developed.

Before vaccination, smallpox epidemics often afflicted virtually all exposed susceptible persons in the population, in other words, all who were not immune because they had survived previous epidemics. Children were the main victims. Depending on the virulence of the strain of smallpox virus, about one child in every eight to twenty would die, and many who survived were left with unsightly scars after the infected blebs on the skin had healed. If the eyes were affected, the result was blindness.

Despite fierce opposition from antivaccination critics, vaccination programs against smallpox began in Europe and the United States in the early nineteenth century, gathering momentum whenever smallpox epidemics occurred, as they continued to do, albeit with declining ferocity, throughout

TABLE 1

the nineteenth and early twentieth centuries. Vaccination against smallpox was not risk-free. It induced fever, painful swelling, and frequently an unsightly scar at the vaccination site. Adverse effects increased in severity with age, strengthening the case for vaccination in childhood. In an epidemic in 1946, the public health authorities in New York City vaccinated about 5 million people over a six-week period–a considerable logistic feat. The human costs included forty-five cases of vaccine-induced encephalitis (severe brain inflammation) and four deaths, along with many thousands of the milder adverse reactions described above. One of the worst possible adverse reactions was a fatal generalized vaccinia infection of the unborn fetus if a pregnant woman was vaccinated.

In 1949 Donald Soper, an American epidemiologist, developed the containment strategy, which consisted of vaccinating all known contacts of every diagnosed case of smallpox rather than indiscriminately vaccinating the entire population. Containment stopped transmission by removing the possibility of the smallpox virus passing from an infected person to others who would have been susceptible in the absence of vaccination, thus reducing the numbers exposed to the risk of adverse reactions. However, in 1965, when the World Health Organization began a vaccination campaign aimed at worldwide eradication of smallpox, total coverage of the entire population in affected countries was the aim. The containment strategy was used later, when the risk of epidemics had declined and the risk of contagion arose mainly from sporadic cases. The last known case of naturally occurring smallpox was a teenage girl in Somalia in 1977. In 1980, the World Health Assembly at its annual meeting declared

TABLE 2

that the vaccination campaign had succeeded and that smallpox had been eradicated from the world.

Other Vaccines

Vaccination against smallpox was the only immunological method of preventing any kind of contagious disease until the rise of scientific bacteriology almost a hundred years after Jenner's experiment. In 1885 Louis Pasteur used an attenuated rabies vaccine to protect a teenage boy, Joseph Meister, after the boy had been bitten by a rabid dog. Before Pasteur's anti-rabies vaccine, rabies was always fatal. By applying Pasteur's methods of developing attenuated strains of pathogens to create innocuous cultures suitable for vaccination, vaccines were soon developed to provide protection against several other previously dangerous diseases of children: diphtheria, tetanus, whooping cough, tuberculosis, and then, with advances in virology and immunology in the middle third of the twentieth century, measles, mumps, poliomyelitis, and others. By the end of the twentieth century, vaccines were available to protect against many diseases that were once a danger to the health and life of infants and children (see Table 1). A high priority for public health science is to develop vaccines for contagious diseases against which so far this preventive method has not been available.

The efficacy of vaccines as a way to protect populations depends on factors that influence herd immunity. For example, diphtheria was a terrible and much feared disease that killed by causing inflammation of the windpipe, so that children who got it often choked to death. After about 50 percent of a population has been immunized (vaccinated) against diphtheria, the probability of transmission to susceptible persons declines sharply. This is called the epidemic threshold.

The epidemic threshold of vaccine-preventable contagious diseases varies according to the infectivity of the pathogen, its mode of spread, and a very large number of

TABLE 3

other variables. Measles used to kill from one in ten to one in a thousand children, depending on their prior state of health, nutrition, and resistance to infection. It remains an epidemic risk until over 95 percent of the susceptible population has been vaccinated. Thus it is important to achieve complete coverage of the susceptible population in measles vaccination campaigns, because those who remain vulnerable can be struck down by dangerous complications such as measles encephalitis (which causes permanent brain damage) as well as by bronchopneumonia, a more common and also dangerous complication. Similarly, vaccination against rubella must reach a very high proportion of women in order to protect all against the small risk that a pregnant woman will get rubella and infect a developing fetus with congenital rubella.

Most vaccines are imperfect; although it is rare, they are sometimes contaminated and tragedies occur. Adverse reactions of varying severity can also occur. The frequency of these reactions has been measured in several large-scale campaigns under the auspices of the World Health Organization (WHO) and the United Nations Children's Fund (UNICEF) (see Tables 2 and 3). However, death and serious disease is a far higher risk without than with vaccination against all the common childhood contagious diseases. Despite the fact that the benefits of vaccination far exceed the risks, resistance continues, occasionally jeopardizing the success of communitywide vaccination programs. For example, vaccination against whooping cough was disrupted in Britain in the late twentieth century when a pediatrician made widely publicized but inaccurate statements about the risks of fatal outcome. It is a challenge for public health authorities, pediatricians, and family doctors to allay the understandable anxiety of parents that their children will suffer harm from vaccination against diseases that have been eliminated from affluent modern societies.

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Vaccination

World of Microbiology and Immunology
COPYRIGHT 2003 The Gale Group Inc.

Vaccination

Vaccination refers to a procedure in which the presence of an antigen stimulates the formation of antibodies. The antibodies act to protect the host from future exposure to the antigen. Vaccination is protective against infection without the need of suffering through a bout of a disease. In this artificial process an individual receives the antibody-stimulating compound either by injection or orally.

The technique of vaccination has been practiced since at least the early decades of the eighteenth century. Then, a common practice in Istanbul was to retrieve material from the surface sores of a smallpox sufferer and rub the material into a cut on another person. In most cases, the recipient was spared the ravages of smallpox. The technique was refined by Edward Jenner into a vaccine for cowpox in 1796.

Since Jenner's time, vaccines for a variety of bacterial and viral maladies have been developed. The material used for vaccination is one of four types. Some vaccines consist of living but weakened viruses . These are called attenuated vaccines. The weakened virus does not cause an infection but does illicit an immune response. An example of a vaccination with attenuated material is the measles , mumps , and rubella (MMR) vaccine. Secondly, vaccination can involve killed viruses or bacteria . The biological material must be killed such that the surface is not altered, in order to preserve the true antigenic nature of the immune response. Also, the vaccination utilizes agents, such as alum, that act to enhance the immune response to the killed target. Current thought is that such agents operate by "presenting" the antigen to the immune system in a more constant way. The immune system "sees" the target longer, and so can mount a more concerted response to it. A third type of vaccination involves an inactivated form of a toxin produced by the target bacterium. Examples of such so-called toxoid vaccines are the diphtheria and tetanus vaccines. Lastly, vaccination can also utilize a synthetic conjugate compound constructed from portions of two antigens. The Hib vaccine is an example of such a biosynthetic vaccine.

During an infant's first two years of life, a series of vaccinations is recommended to develop protection against a number of viral and bacterial diseases. These are hepatitis B, polio, measles, mumps, rubella (also called German measles), pertussis (also called whooping cough), diphtheriae, tetanus (lockjaw), Haemophilus influenzae type b, pneumococcal infections, and chickenpox. Typically, vaccination against a specific microorganism or groups of organisms is repeated three or more times at regularly scheduled intervals. For example, vaccination against diphtheria, tetanus, and pertussis is typically administered at two months of age, four months, six months, 15–18 months, and finally at four to six years of age.

Often, a single vaccination will not suffice to develop immunity to a given target antigen. For immunity to develop it usually takes several doses over several months or years. A series of vaccinations triggers a greater production of antibody by the immune system, and primes the antibody producing cells such that they retain the memory (a form of protein coding and antibody formation ) of the stimulating antigen for along time. For some diseases, this memory can last for a lifetime following the vaccination schedule. For other diseases, such as tetanus, adults should be vaccinated every ten years in order to keep their body primed to fight the tetanus microorganism. This periodic vaccination is also referred to as a booster shot. The use of booster vaccinations produces a long lasting immunity.

Vaccination acts on the lymphocyte component of the immune system. Prior to vaccination there are a myriad of lymphocytes. Each one recognizes only a single protein or bit of the protein. No other lymphocyte recognizes the same site. When vaccination occurs, a lymphocyte will be presented with a recognizable protein target. The lymphocyte will be stimulated to divide and some of the daughter cells will begin to produce antibody to the protein target. With time, there will be many daughter lymphocytes and much antibody circulating in the body.

With the passage of more time, the antibody production ceases. But the lymphocytes that have been produced still retain the memory of the target protein. When the target is presented
again to the lymphocytes, as happens in the second vaccination in a series, the many lymphocytes are stimulated to divide into daughter cells, which in turn form antibodies. Thus, the second time around, a great deal more antibody is produced. The antibody response also becomes highly specific for the target. For example, if the target is a virus that causes polio, then a subsequent entry of the virus into the body will trigger a highly specific and prompt immune response, which is designed to quell the invader.

Most vaccinations involve the injection of the immune stimulant. However, oral vaccination has also proven effective and beneficial. The most obvious example is the oral vaccine to polio devised by Albert Sabin . Oral vaccination is often limited by the passage of the vaccine through the highly acidic stomach. In the future it is hoped that the bundling of the vaccine in a protective casing will negate the damage caused by passage trough the stomach. Experiments using bags made out of lipid molecules (liposomes) have demonstrated both protection of the vaccine and the ability to tailor the liposome release of the vaccine.

The nature of vaccination, with the use of living or dead material that stimulates the immune system, holds the potential for side effects. For some vaccines, the side effects are minor. For example, a person may develop a slight ache and redness at the site of injection. In some very rare cases, however, more severe reactions can occur, such as convulsions and high fever. However, while there will always be a risk of an adverse reaction from any vaccination, the risk of developing disease is usually far greater than the probability of experiencing severe side effects.

See also Adjuvant; Anti-adhesion methods; Immune stimulation, as a vaccine

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vaccination

The Columbia Encyclopedia, 6th ed.

Copyright The Columbia University Press

vaccination, means of producing immunity against pathogens, such as viruses and bacteria, by the introduction of live, killed, or altered antigens that stimulate the body to produce antibodies against more dangerous forms. Vaccination was used in ancient times in China, India, and Persia, and was introduced in the West in 1796 by Edward Jenner. Jenner demonstrated that rubbing or scraping the cowpox virus (the term vaccine comes from the Latin vacca, cow) into the skin produced only a local lesion but was sufficient to stimulate the production of antibodies that would defend the body against the more virulent smallpox.

Vaccination has eradicated smallpox worldwide and prevents such diseases as cholera, rabies, and typhoid fever. Vaccines work with the immune system's ability to recognize and destroy foreign proteins (antigens) that it determines are
"nonself."
Scientists are using this same principle to help the body recognize antigens peculiar to cancer cells. It is also applied in an experimental birth control vaccine that tricks the immune system into believing that human chorionic gonadotropin (HCG), a hormone secreted by a developing fertilized egg, is foreign, thus inactivating it and inducing menstruation even if fertilization has occurred. Vaccines are also used to control animal pests by conferring temporary infertility.

Vaccination programs have been notably successful in the United States. For example, in 1998 the Centers for Disease Control and Prevention reported only one case of poliomyelitis, one of diphtheria, 34 of tetanus, and 89 of measles. Despite the availability of vaccines, many thousands of people in the United States still die each year from vaccine-preventable diseases such as hepatitis and influenza.

Immunization against 17 diseases is recommended for young children and adolescents: hepatitis B (HepB); rotavirus; diphtheria, tetanus (lockjaw), and pertussis (whooping cough), given together as DTaP (formerly DTP) and, for older children, Tdap; Haemophilus influenzae b (Hib); poliomyelitis (IPV); pneumococcal infections, including pneumonia, meningitis, and bacteremia (PCV and PPV); measles, mumps, and rubella, given together as MMR; chicken pox (Var); hepatitis A (HepA); influenza; Neisseria meningitidis (meningococcal meningitis; MCV4, MPSV4); and human papillomavirus (HPV). Researchers are working to develop combination vaccines that would simplify vaccine administration. Immunization against diseases such as yellow fever may be necessary before traveling to some countries. In 2002 the U.S. government decided to reinstitute smallpox vaccination for many military, health-care, and emergency personnel because of concern about a possible bioterror attack using smallpox.

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vaccination

vaccination, a term first used by Jenner (1798) for inoculating cowpox matter (vacca = cow) to produce immunity from the far more virulent smallpox, has since come to mean the creation of immunity from infectious diseases in general. Its benign effect on death rates from smallpox led to gradual abandonment of earlier techniques, but not without opposition. The 1840 Vaccination Act prohibited inoculation and permitted vaccination of the poor at ratepayers' expense; the 1853 extension made the practice compulsory, though it was not universally enforced. An organized movement to repeal compulsory vaccination developed after 1871, leading eventually to amendments of previous statutes (1898). Nevertheless, with compulsory notification of infectious diseases and better trained public health officers, vaccination and revaccination rapidly reduced the prevalence, morbidity, and mortality of smallpox. Subsequent vaccines (using attenuated or altered viruses) against diphtheria, polio, measles, whooping cough, and rubella have largely controlled these diseases.

A. S. Hargreaves

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vaccinate

vac·ci·nate / ˈvaksəˌnāt/ • v. [tr.] treat with a vaccine to produce immunity against a disease; inoculate: all the children were vaccinated against diphtheria.DERIVATIVES:vac·ci·na·tion / ˌvaksəˈnāshən/ n.vac·ci·na·tor / -ˌnātər/ n.

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vaccination

vaccination (vak-si-nay-shŏn) n. a means of producing immunity to a disease by using a vaccine. The name was applied originally only to treatment with vaccinia (cowpox) virus, which gives protection against cowpox and smallpox. However, it is now used synonymously with inoculation as a method of immunization against any disease.

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